This invention relates generally to optical scanners, and, more particularly, to an optical scanner which is capable of being utilized in conjunction with a laser system, and in an area which is either confined or highly restrictive in size.
With the advent of the miniaturization of many optical systems such as, for example, those found in missiles, it is becoming increasing necessary to scale down the optical components of such systems so as to readily fit within and operate reliably within highly confined or restrictive areas. The scanning of optical beams emanating from a laser system in order to project the beam to some region external of the scanning device through, for example, a window within a missile, places a size limitation upon the scanning device. Particularly, in the use of a long slender missile, the scanning device must be located within the extremely confined location of the nose cone of the missile.
In general, scanning devices which provided a definite fixed high scan frequency were in the form of resonant reflector scanners or rotary reflector polygons. In either case, these devices required clearances for the mirror elements thereof to fold the optical beam path into usually restrictive spaces. If it became desirable to cover large scan angles, large windows were generally required in the customary scanner configurations because the mechanism which produced the angle scan was situated in a position remote from the window. This was especially true of rotary polygon reflector scanners. In such cases, the facets of the polygon were designed large in comparison with the scanned optical beam so that most of the optical energy could be scanned over the required angular field.
As an example, an octagon reflector which is capable of scanning an optical beam through a maximum of 90.degree. range required an optical aperture diameter of 50 mm, and (p-1)/p of the scanned field must be covered by the full 50 mm aperture, which therefore requires the facet width to be p times the optical aperture. Consequently, (p-1)/p=2/3 of the scan angle at full aperture and requires the facet to be of a width equal to 3.times.50=150 mm. The diameter of the octagon (for 2/3.times.90=60.degree. full aperture coverage) must then be in the area of 392 mm.
The "exit pupil" of this type of scanner is the facet of the octagon. If the window could be placed very near this position then the window size could be 50 mm by 150 mm. But, if the scanner must be contained within, for example, the nose cone of a missile of normal shape then the angular coverage of the optical beam would necessitate the utilization of a very wide window. Consequently, the scanning devices in use today are incapable of handling the scanning requirements of laser systems when utilized in confined or restrictive locations.
It would be highly desirable to provide an optical scanner which is not only reliable in its operation and capable of handling high scan frequencies but is also capable of being situated within a confined space without placing burdensome restrictions upon the optical system with which it is utilized.